1. Field of the Invention
This invention generally relates to a bicycle transmission. More specifically, the present invention relates to a bicycle transmission in which an endless drive member or chain remains substantially in a single plane.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle transmission.
One of the most popular types of bicycle transmissions utilizes a plurality of sprockets mounted on the hub of a rear wheel. A rear derailleur is utilized to shift a chain between adjacent sprockets. The rear derailleur is typically operated by an operating lever or control mechanism that is mounted on the handlebar of the bicycle. Thus, the rider can selectively change gears by operating the operating lever which in turn causes the rear derailleur to shift the chain between various sprockets. This type of transmission is typically also provided with a front derailleur for shifting the chain between a plurality of chain wheels. While these type of typical transmissions work very well, these types of bicycle transmissions require the chain to be pushed or pulled in a transverse direction of the bicycle. In other words, in this type of bicycle transmission, the chain line of the chain never remains constant. Rather, utilizing a derailleur system, the chain must be bent to some degree in either direction which is parallel to the chain pins. Over an extended period of time, this bending of the chain causes the chain to be damaged. Thus, the life span of the chain is reduced.
Moreover, in most conventional bicycle transmissions that utilize a derailleur system, the rear derailleur is located below the rear hub. This exposes the rear derailleur to dirt and debris from the wheel. Thus, the rear derailleur can become excessively dirty and stop shifting properly. Moreover, the location of the rear derailleur is prone to being hit by objects during riding. Also, the rear derailleur is often damaged if the bicycle falls over. Thus, a transmission located at the rear hub has several potential disadvantages.
In addition, the rear wheel is often mounted on a suspension where the rear wheel swings up and down when traveling over rough terrain, such as in the case of a free ride or downhill type bike with eight inches of rear wheel travel. Thus, in these conventional derailleur type transmissions that are at least partially disposed at the rear wheel, these conventional derailleur type transmissions are shaken and swung up and down violently with the rear wheel. This can significantly decrease the operation and durability of the drive train. Further, conventional derailleur type transmission has considerably more unsprung weight than a rear wheel without derailleur type transmission mounted thereto.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle transmission. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.